It is well known in the art of producing synthetic resins to react a polyol or a polyamine (or a compound containing both hydroxyl and amine functionalities) with a polyisocyanate in the presence of a catalyst, such as a tertiary amine, a metal catalyst (e.g. tin) or the like to give a cross-linked resin having polyurea groups. The resulting reaction products are known as flexible polyurethane foams, semi-rigid foams, rigid foams or elastomers, spray polyurea and the like. Polyurea reaction injection molded (RIM) materials and reinforced RIM (RRIM) products containing embedded glass, metal or plastic reinforcing fibers may be made by reacting a polyamine and a polyisocyanate in a heated mold under pressure optionally with a catalyst.
A common problem encountered when molds are employed to shape the article made, particularly when RIM systems are used, is having the components react together at a rate appropriate to the filling of the mold. That is, if an automotive body panel is being fabricated, for example, the components should preferably not start reacting together until the entire mold is filled with the mixture. If reaction occurs prematurely, the RIM material will set up or "gel" in part of the mold and prevent the liquid material from filling the mold resulting in an incomplete part. In one aspect of the invention, it is desirable that the system have longer "flow times" or longer time to flow the components into the mold in a mixed state before reaction occurs. At the same time, the reaction should not take too long once begun since it is desirable to cycle parts through the mold at as high a speed as possible to reduce production costs.
Thus, it would be desirable if a RIM system or components therefor could be devised which would delay the reaction of the materials until the mold is completely filled, but which would not otherwise adversely affect the process.